1. Field of the Invention
One embodiment of the present invention relates to a display device for displaying an image.
2. Description of the Related Art
A variety of portable electronic devices, such as a cell phone, a smartphone, a personal computer, a tablet terminal, a portable game machine, and a portable music player, have recently come into widespread use. More intuitively operable electronic devices can be obtained by providing a touch sensor over a display portion for image display as an interface of such portable electronic devices.
In the display portion, a light-emitting device including an organic electroluminescent (EL) element, a liquid crystal display device, an electronic paper performing display by an electrophoretic method, or the like can be typically used.
For example, in a basic structure of an organic EL element, a layer containing a light-emitting organic compound is provided between a pair of electrodes. By applying voltage to this element, light emission from the light-emitting organic compound can be obtained. A display device including such an organic EL element needs no backlight which is necessary for liquid crystal display devices and the like; therefore, thin, lightweight, high contrast, and low power consumption display devices can be obtained. For example, Patent Document 1 discloses an example of a display device including an organic EL element.
Typical touch sensors are of resistive type and of capacitive type; besides, a variety of types such as a surface acoustic wave type and an infrared type are known.